The swim bladder is a gas-filled organ found in many bony fish, allowing them to maintain buoyancy in water. By adjusting the amount of gas in the swim bladder, fish can rise or sink without expending energy. This adaptation helps them conserve energy while swimming and aids in their ability to find food and avoid predators. Not all fish have a swim bladder; for example, sharks and rays rely on other methods for buoyancy, such as their large livers filled with oil. The swim bladder also plays a role in sound production and hearing for some species, enhancing their communication and environmental awareness.